(a) Field of the Invention
The present invention relates to a spool case for storing and carrying a bonding wire of a wire bonding assembly used in manufacturing a semiconductor chip package and a method of handling a spool using the same. More particularly, the invention relates to a bonding wire spool case and a method of handling a spool using the same which can effectively prevent the durability and the holding of the spool from being deteriorated due to the repeated coupling and decoupling operations of the spool with respect to the spool holder, and prevent the bonding wire from being contaminated and damaged due to the carelessness of the worker.
(b) Description of the Related Art
Generally, a wire bonding assembly is a device for electrically connecting a lead of a lead frame to a bonding pad of a semiconductor chip bearing an electrical characteristic by way of a conductive wire such as a high purity platinum Pt wire or an aluminum wire.
The wire bonding assembly is usually provided with a spool, a spool holder, a wire feed guider, a wire clamp, and a capillary. A conductive wire is wound on the spool, and the spool is fitted to the spool holder. The conductive wire is fused by way of the capillary and a torch bar, and welded to the bonding pad of the semiconductor chip and the lead
In the wire bonding assembly, the spool wound with a conductive metal wire thereon is usually placed within a spool case, and in that state, it is stored and carried while preventing the contamination and damage thereof. Various kinds of spool cases are used for that purpose.
For instance, Japanese Utility Model Publication Number Sho 54-103747 discloses a spool case having a base with a protrusion onto which a cylindrical spool is inserted, and a cover coupled to the base to prevent a foreign material, such as dust, from being introduced. The cover is provided with a spool case, which has a depressed portion for receiving the spool in correspondence with the protrusion of the base.
The worker grips the flange portion of the spool by hand, and fits it to the spool holder to bring out the spool from the spool case.
Accordingly, with the handling of the spool, the fingers of the worker contact the surface of the conductive wire. In this case, the wire is contaminated and damaged, and this induces serious device failures during the wire bonding process.
Japanese Patent Publication Laid-open No. 2000-012599 discloses a bonding wire spool case having an interfacial coupling member externally fitted around the spool flange to hold the spool, and a base capable of being elastically transformed. The worker presses both lateral sides of the base while elastically transforming the base to remove the spool from the spool case.
However, with the spool case disclosed in Japanese Patent Publication Laid-open No. 2000-012599, the base is formed with a material capable of being elastically transformed such that the spool can be separated from the spool case by way of the interfacial coupling member.
Accordingly, in case the base repeatedly suffers the elastic transformation to make coupling or decoupling of the spool, stress is concentrated at a predetermined region of the base due to the elastic transformation. Consequently, the base is stress-damaged while being deteriorated in its durability.
The interfacial coupling member, which is connected to the base in a body to substantially hold the spool, is formed with an elastic plastic material. With the repeated uses, the interfacial coupling member becomes worn out or blunt, and this deteriorates reliability in the spool holding operation.
Furthermore, with the handling of the spool, the worker picks out the cover from the base, and grips the base to mount the spool to the spool holder of the bonding machine. At this time, the worker may carelessly grip both sides of the base. In this case, the spool holding state of the interfacial coupling member is released so that the spool is separated from the base. Consequently, the bonding wire is contaminated, and damaged.